This invention generally relates to the filed of intravascular balloon catheters, and more particularly to a balloon catheter with a balloon having a variable radial force along the longitudinal axis for improved expansion and stenting.
Percutaneous transluminal coronary angioplasty (PTCA) is a widely used procedure for the treatment of coronary heart disease. In this procedure, a balloon dilatation catheter is advanced into the patient's coronary artery. The balloon on the catheter is inflated within the stenotic region of the patient's artery, exerting radial force on the stenotic region, to open up the arterial passageway. Thereby increasing the blood flow.
To facilitate the advancement of the dilatation catheter into the patient's coronary artery, a guiding catheter having a preshaped distal tip is first percutaneously introduced into the cardiovascular system of a patient by the Seldinger technique through the brachial or femoral arteries. The catheter is advanced until the preshaped distal tip of the guiding catheter is disposed within the aorta adjacent the ostium of the desired coronary artery, and the distal tip of the guiding catheter is then maneuvered into the ostium. A balloon dilatation catheter may then be advanced through the guiding catheter into the patient's coronary artery until the balloon on the catheter is disposed within the stenotic region of the patient's artery. The balloon is inflated, exerting radial force on the stenotic region, opening up the arterial passageway and increasing the blood flow through the artery.
Generally, the inflated diameter of the balloon is approximately the same diameter as the native diameter of the body lumen being dilated so as to complete the dilatation but not over expand the artery wall. After the balloon is finally deflated, blood flow resumes through the dilated artery and the dilatation catheter can be removed therefrom. However, damage to the vessel wall at and around the stenosis can result from the expansion of the balloon against the vessel wall.
In such angioplasty procedures, there may be a restenosis, i.e. reformation of the arterial blockage. To reduce the restenosis rate and to strengthen the dilated area, physicians frequently implant an intravascular prosthesis, called a stent, inside the artery at the site of the lesion. Stents may also be used to repair vessels having an intimal flap or dissection or to generally strengthen a weakened section of a vessel. Stents are usually delivered to a desired location within a coronary artery in a contracted condition on a balloon of a catheter which is similar in many respects to a balloon angioplasty catheter, and expanded to a larger diameter by expansion of the balloon. Thereafter, the balloon is deflated to remove the catheter and the stent is left in place within the artery at the site of the dilated lesion.
Stents have been used to open a stenosed vessel for some time. Unfortunately, the force needed to move against the thick stenosis causes the balloon to expand against the vessel wall in the area proximal and distal to the stenosis. The expansion of a stent against the vessel wall can cause damage to the vessel wall, similar to the damage caused by expansion of the balloon.
Therefore, what has been needed is a balloon catheter with improved expansion characteristics to avoid damage to the vessel wall. The present invention satisfies these and other needs.